The chief U.S. district judge for Washington D.C. suddenly resigned Wednesday as news surfaced of a sex-abuse lawsuit filed against him by a Utah woman.

The lawsuit filed in Salt Lake City by Terry Mitchell accuses Judge Richard W. Roberts of repeatedly raping her when she was a witness in a 1981 federal trial and he was a federal prosecutor handling civil-rights cases.

She was 16 at the time, the lawsuit says, though this was old enough to consent under Utah’s statutory-rape laws at the time.

Judge Roberts, who was appointed to the federal bench in 1998 by President Bill Clinton, was 27 at the time of the trial.

His lawyers said in a statement cited by the National Law Journal that a consensual “intimate relationship” took place but claims of sexual assault are “categorically false.”

According to the Washington Post, he resigned Wednesday evening for “unspecified health reasons.” He also maintained that the relationship took place after the trial.

Ms. Mitchell was an eyewitness in the trial of Joseph Paul Franklin, a white supremacist serial killer who was executed in 2013 in another case. Ms. Mitchell, who is white, was one of two women jogging with two black men whom Franklin killed.

“According to the suit, Mitchell was already the victim of sexual assault by several other men, including her step-grandfather, and in his role as a prosecutor, Roberts had access to her mental counseling records,” NBC News reported.

In a statement Wednesday, Rep. Jason Chaffetz, Utah Republican and chairman of the House Oversight and Government Reform Committee, said his panel had recently learned of the charges from the Utah state attorney general’s office.

“We will work with the House and Senate Judiciary Committees to determine next best steps to ensure justice is served,” Mr. Chaffetz said.